This invention relates generally to gas turbine engines and, more particularly, to determining operating parameters for controlling gas turbine engines.
In at least some known rotatable machines for example, a gas turbine engine, turbine blade and/or nozzle temperatures have to be limited to ensure safe operation of the gas turbine engine and to ensure desired life for engine components. However, because of the adverse environments where these components operate, the temperatures are not measurable using thermocouples or RTDs, the traditional techniques for measuring gas path temperatures.
One known technique used on current production engines involves measuring exhaust gas temperature (EGT) downstream of the high-pressure turbine components at a location cool enough for a temperature probe to survive. This technique is prone to sampling problems, thermal lags in the probes, and errors in correlating the measured gas temperature to the desired metal temperature upstream. Moreover, as gas-path temperatures increase, probe life is reduced and cost increases. A second measurement technique uses a pyrometer to measure the metal temperature of interest. This technique is expensive and is subject to problems with line of sight, lens fogging, and sensing system unreliability.